Oil circuit breaker



Filed. March 4, 1959 ew@ Si lio Patented Dec; 3, .1940

on. clacUI'r naEAxEn Giuseppe Scarpa, Savona, Italy Application March 4, 1939, Serial No. 259,873

In Italy March 9, 1938 v ZCiaims.

'I'his invention relates to 'oil circuit. breakers for high-voltage alternating current of the type employing a reduced oil volume and breaking boxes. An object of4 this invention is to improvel said .boxes in order to reduce the power dissipated in the breaking arc and stresses transmitted to the'oil circuit breaker unit. L

A further object of this invention is to provide the breaking box on the side oi the stationary eye-shaped contact opposite the arc zone with an opening through which part of the vapours produced by the arc, mainly the hottest vapours, are discharged. A further object oi' this invention is to damp the expansion of the vapours and reduce the shock transmitted to the walls of the main breaker tank by providing a tube of insulating material which surrounds the portion of the arc set up outside the breaking box.

A further object of this invention is to provide a circuit breaker of the type referred to above, by which itv is possible to break the circuit of a transmitting line for extinguishing arcs and thereupon immediately re-establish the circuit, in order to prevent synchronous generators connected in said circuit to come out of parallelism. with a maximum `breaking period of 116 second. For this purpose each movable contact of the circuit breaker comprises two opposite contact plugs arranged to successively cooperate withl breaking boxes at the end of the stroke io1' the movable contact in one direction and in the opposite direction, respectively.

rThe accompanying drawing shows 'by way of examplel a construction of the oil breaker according to my invention/ Figure 1 is an axial vertical section.

Figure 2 isa cross vertical section on anenlarged scale ofthe breaking box.

Figure 3 is a horizontal section thereof.

Figure 4 is an axial vertical section of a circuit breaker, by means of which'lt is possible to open and close circuits in a rapid sequence.

Referring to the drawing, I denotes the tank of insulating material of an oil breaker.

The tank I encloses the breaking boxes 2 car\ rying the stationary contacts cooperating with the movable contacts 3, supported by pairs oi' sleevesof conducting material 4 slipped ona shaft 5 oi.' insulating material rotatably mounted in supports eccentrically arranged in the cover plate I0 between the arc zone and the portion of the l0 tank situated behind the box. Y

A sleeve I3 of insulating material is arranged outside the front portion of the box inI alignment with the hole 6 anda certain distance therefrom and is supported by the Iplate lIl secured to the .1l foot I5 of the stationary contactl I2. i

As the movable contact 3 isreleased from the eye I I on breaking, an arc is formed which vapo-A rises a. portion of the oil and the gases produced exert a pressure on the oil contained in the lower 20' portion of the box, causing it to rise in the conduit 8 and flow through the arc, when the movable contact is withdrawn from the box. To ensure an actual andeiiicient oil ilow through the e arc, the jet of pressure gas issuing from the holegs t should not be too violent. I obtainshis by providing a rear hole I0 which allows a portion of the gases to escape, thereby reducing the pressure in the box 2 and violence of the gas jet through the hole 6. l Moreover, the rear hole III is directly 30 in conmunication with the central portion of the gas bubbles and discharges the gas portion nearer the arc zone, which is the hotter portion, thusv improving the deionising action of the oil from the conduit 8. 35

When the arc extends beyond the hole 6, the prompt vaporisation of oil on its contact therewith produces a very rapid movement of the oil which is still further accelerated by the rapid expansion of the gas; this" objectionable action o is lessened by the sleeve I3 which damps the gas expansion, thereby reducing the shock transmitted to the tank I enclosing the above described unit.

The advantageous effect of the` sleeve I3 is 45 more particularly effective when a number of breaking boxes are arranged in one tank, more particularly in the case Aof coupled breaking boxes, as in the case of quick opening and closing circuit breakers as shown in Figure 4. Each 50 movable contact comprises two plugs 20 and 2| adapted to cooperate with the breaking boxes 22 and 23, respectively, of which the stationary contacts are connected -to one lead 24. The

shaft 25, on which the movable contacts .are 55 e, mountedfis provided externally of the tank 26 with a pinion 21 meshing lwith a rack 28 to which is imparted ari altennatirig motion by means of a twin-coli electromagnet 29.

A spring 30 connected to an arm 3l secured to the shaft 25 and anchored at 32 to a stationary part of the tank 26 tends to return the movable contacts at half-length of their stroke and to maintain them in theiropen position.

, As the rotating contacts open. they break the circuit over a series of stationary contacts and as they reach the endl of their stroke they re'- close the circuit over another series of stationary contacts.

. The above described circuit breaker may be held in its open position through the spring 3l! and may perform a similar function as the type shown in Figures 1 to 3. v

I `wish to be vunderstood -that I doV not desire to -be limited tothe exact-details of construction shown and described, for obvious modifications will occur to a person skilled in the-art.-

1. Anv oil circuit breaker comprising. a tank of\ insulating material lled with oil, breaking `boxes immersed in the oil of said tank, a stationary eye-shaped contact in each of said boxes,

the front'and rearjwalls of said boxes having holes therein in alignment with the hole in said contact, a shaft rotatably mounted in said tank,l

4movable plug contacts carried by said shaft and insulated thereon and arranged to cooperate n lwith each of said vcontacts through one of the 2. An oil circuit breaker comprising a tank y of insulating material filled with oil, a. plurality of coupled breaking boxes immersed in the oil of said tank, eye-shaped contacts in each oi said boxes, the opposite walls of said boxes having holes therein in alignment with the. holes in said stationary contact, a shaft rotatably mounted in said tank and a plurality of movable contacts each having two opposite plugs, one of said vplugs 'being adapted to engage` with the stationary contact in one of said coupled boxes through one of said holes at the end of the stroke of the movable contacts in one direction and the other plug being adapted to engage the stationary contact in the other of'said coupled boxes throughgone of said holes in the boxes at the end ofthe stroke o! the movable contacts in the opposite direction, an outer tubular expansion conduit on each of said boxes with the axis thereof perpendicular to the common axis of the hole in the stationary contacts and of the holes in the box walls, said` tubular expansion conduit communicating at one end with the bottom of the box and opening at its other end near the axis 'of said holes, a protecting sleeve in said tank outside each box adjacent and in alignment with the front hole in said box.` and isaid plug contacts moving through the associated sleeve.

GIUSEPPE SCARPA. 

